This paper assesses reactive gliosis in the optic tracts and other regions of brain in Lewis rats with experimental autoimmune encephalomyelitis (EAE). Enhanced immunostaining for glial fibrillary acidic protein (GFAP) in brains from rats with EAE occurred primarily in the white-matter tracts and was not restricted to sites of inflammation. Immunocytochemical staining for other putative astrocytic antigens demonstrated glutathione-S-transferase (Yb isoenzyme) to be localized extensively in GFAP-positive cells and vimentin to be present both in inflammatory cells and in some GFAP-positive astroglial cells. Positive staining for carbonic anhydrase and glutamine synthetase was observed in oligodendrocytes. In the optic tracts glutamine synthetase, but not carbonic anhydrase, was also observed in some astrocytes.